This invention relates to communications, and more particularly relates to systems and methods for supporting Caller Identification and related information delivery through networks incompatible to an in-band transmission of the Caller Identification information such as a wireless local loop system.
Wireless local loop systems represent a significant improvement in telephone service by providing customers alternative access to public telephone networks. Users can continue to use familiar and convenient conventional telephone equipment yet communicate over a wireless communication link. A customer premises radio unit (CPRU) provides the interface between the conventional telephone equipment and the wireless communication link.
A number of technical challenges must be overcome, however, to successfully interface a conventional phone to a wireless communication link. For example, in a wireless environment, the digits in a complete telephone number are only transmitted to the central office after the user presses a SEND button or its equivalent. In contrast, conventional telephone equipment transmits the digits as they are dialed to the central office. Thus, a wireless local loop system may be required to, after generating a dial tone, perform digit analysis to determine that a complete telephone number has been dialed.
Another technical challenge involves delivery of Caller Identification (Caller ID or CID) in the wireline to wireless environment present in wireless local loop systems. Caller ID in a wireline environment is sent as an in-band transmission using FSK (frequency shift key) modulation. Caller ID is the generic term for several features that are a member of the Bellcore CLASS family of telephone services offered by local telephone companies for a monthly fee. Providing these services depends on the presence of Signaling System 7 (SS7) end-to-end in the network. SS7 is the signaling protocol used to communicate between central office switches. In the U.S. and Canada, Caller ID follows primarily the Bellcore documents GR-30-CORE (on-hook and off-hook data transmission), TR-NWT-000031 (Calling Number Delivery), TR-NWT-001-188 (Calling Name Delivery Generic Requirements), and TR-NWT-000575 (Calling Identity Delivery on Call Waiting). In a wireless local loop environment, such an FSK-modulated signal would be garbled upon transmission through the vocoders which are required at either end of the wireless transmission (for example, the base station and the CPRU). It is to be noted that other environments wherein an FSK-modulated Caller ID signal must be transmitted through an incompatible network will also encounter this problem. There is a need in the art for a wireless local loop system that is able to deliver Caller ID information to a conventional telephone despite the in-band nature of the Caller ID transmission.
The present invention comprises systems and methods for delivery of Caller ID information in suitable environments. These environments require the transmission of an FSK-modulated Caller ID signal from a Central Office (CO) to a telephone wherein a network incompatible to an in-band transmission of the Caller ID signal intervenes between the CO and the telephone. A first network component of the incompatible network couples to the CO, and a second network component of the incompatible network couples to the telephone. In the incompatible network, the first network component converts the FSK-modulated Caller ID signal received from the calling party into an out-of-band message for transmission over the incompatible network. The second network component receives the out-of-band message and converts the message into an FSK-modulated Caller ID signal for delivery to the called party. The present invention contemplates both on-hook and off-hook delivery of Caller ID information.
The present invention comprises two main embodiments for on-hook delivery of Caller ID information. In the first embodiment, denoted as xe2x80x9csecond network component directed,xe2x80x9d the call flow proceeds until the second network component would ring the line of the called party. The second network component seizes the line but does not apply a ringing signal. Although the line is not ringing, the second network component continues with the call flow as though the second network component had entered the silent interval after the first ring cycle at the called party. Subsequently, the CO transmits the FSK Caller ID information to the first network component which detects the FSK transmission and converts it into an out-of-band message and transmits the out-of-band message over the incompatible network to the second network component. Upon receipt of this out-of-band message from the first network component, the second network component converts it back into an in-band FSK Caller ID message, applies the first ring to the line and delivers the FSK message during the first silent interval between rings longer than three seconds. When the phone of the called party goes off-hook, voice traffic is established in a standard manner.
In the second embodiment for on-hook delivery of Caller ID information, denoted as xe2x80x9cfirst network component directed,xe2x80x9d the first network component, without sending signals to the second network component, initiates a call flow to the CO as though the second network component were entering the silent interval between the first and second rings. Subsequently, the CO transmits the FSK Caller ID information to the first network component which detects the FSK transmission and converts it into an out-of-band message. After a communication link has been established between the first network component and the second network component, the Caller ID information is transmitted in an out-of-band message. The first network component may then begin ringing the line and transmitting the Caller ID message, after conversion into the FSK format, in the first silent interval.
One example of a network incompatible to an in-band transmission of FSK-modulated Caller ID signals is a wireless local loop system. A wireless local loop system provides a wireless link between customer premises equipment (CPE) and the public switched telephone network (PSTN). In wireless local loop systems, a number of different protocols may be used at the first and second network units. For example, the first network component may communicate with the CO of a public switched telephone network under a GR-303 protocol. The first and second network components may communicate with each other through a wireless network under, for example, a DECT or a GSM protocol. In one wireless local loop embodiment of the present invention, the CPE links to a customer premises radio unit (CPRU) which serves as the second network component. The CPRU communicates over the wireless link to a base station. In turn, the base station may be controlled by a radio node controller (RNC) that serves as the first network component. The RNC connects to the public switched telephone network containing the central office (CO). With respect to this wireless local loop, the xe2x80x9cfirst network component directedxe2x80x9d embodiment would thus be an xe2x80x9cRNC directedxe2x80x9d embodiment and the xe2x80x9csecond network component directedxe2x80x9d embodiment would be a xe2x80x9cCPRU directedxe2x80x9d embodiment.
On hook delivery of a Visual Message Waiting Indication (VMWI) is also provided for by the present invention. In this embodiment, an over the air connection is established between the first and second network components. Upon establishing the over the air connection, the first network component transmits the connection status to the CO which transmits the FSK-modulated VMWI information to the first network component. The first network component converts the FSK-modulated VMWI information into an out-of-band message and transmits it to the second network component. The second network component converts the out-of-band message back into an FSK-modulated VMWI form and transmits it to the called party.
The present invention also contemplates delivery of Caller ID during Call Waiting (CIDCW) while the phone of the called party is off-hook and an active call is in progress. An audible Subscriber Alerting Signal (SAS) and a CPE Alerting tone (CAS) are transmitted by the CO to the CPE and the Caller ID display device, respectively. After acknowledging receipt of the CAS, the Caller ID display device mutes the voicepath and begins a timer. Receiving this acknowledgement, the CO delivers the FSK-modulated Caller ID information to the first network component which converts the Caller ID information into an out-of-band message. The second network component, upon receipt of this out-of-band message, transmits another CAS signal to the Caller ID display device which by now will have timed-out. The CID display device again acknowledges receipt of the CAS signal and mutes the voicepath. After conversion of the out-of-band message into an FSK-modulated Caller ID message, the second network component transmits the Caller ID message to the Caller ID display device and then restores the voice path.
The above and other features and advantages of the present invention will become apparent from the following description and figures.